1. Field
The following description relates to a reference signal generation and a power factor compensation technique. The following description also relates to a reference signal generating circuit and a power factor compensation apparatus that measures a phase for an input signal of a power converter, in order to generate a reference signal having a specific amplitude and in order to improve power factor correction.
2. Description of Related Art
A power converter converts inputted power into another, outputted power, such as an outputted power having a different current, voltage or frequency. For example, the power converter receives inputted power to provide outputted power to a load, for example, a LED lamp. Herein, the inputted power may correspond to an alternating current AC power and the outputted power may correspond to a direct current DC power.
A waveform of a current flowing into the load is similar to that of a current of the inputted power. However, a reactive power loss may occur due to a phase difference between a voltage and a current of the inputted power.
In order to decrease the reactive power loss and to improve a power factor correction of the power converter, the phase difference between a voltage and a current of the inputted power may be decreased.
Some power converters perform a full-wave rectification on an inputted alternating current power source to generate an input voltage and sense the input voltage to generate a reference signal. Such power converters compare the reference signal and the current flowing into the load to control a level of the current flowing into the load based on the reference signal. The reference signal is varied according to the input voltage. Accordingly, a level of the current flowing into the load is varied according to the reference signal. Therefore, a frequency and a phase for the current flowing into the load are similar to those of the input voltage. For example, when the input voltage corresponds to a sine wave, the input current waveform becomes similar to a sine wave. As a result, the phase difference between a voltage and a current of the inputted power may be decreased, as discussed above.
However, when such power converters use a resistor element in order to detect the input current, it may be difficult to integrate a control unit for controlling the power converter into the architecture of the power converter due to difficulties of integrating resistors that resist a high input voltage.
FIG. 1 is a waveform diagram illustrating a reference signal that is generated by a power converter. Referring to FIG. 1, the power factor correction circuit approximately measures a single period, such as T1 through T3, to generate a corresponding reference clock RCLK signal. Therefore, the power factor correction circuit generates a sine wave SREF programmed in a digital/analog converter (D/A converter), based on the generated reference clock RCLK.
In the power factor correction circuit, an error of the reference clock RCLK may occur due to an error of single period information, such as T1 through T3. However, a correction for the error in the D/A converter is not performed and a distortion between the input voltage Vin and the sine wave SREF occurs according as the sine wave SREF programmed regardless of how the input signal Vin is generated.